Are there charts illustrating allowable HVAC duct sizes that can fit between truss chords for various truss depths?
Per Stuart Lewis from Alpine Engineered Products: For a standard 4×2 floor truss (meaning Warren-style webs with 30-inch panels) with double-cut webs, the maximum round duct in the end panel is 5.625, 6.5, and 7.25 inches for 12, 14 and 16 inch truss depths, respectively. By end panel, I mean the 15-inch long panel formed by the outermost diagonal and the end vertical, where the duct would be against the end vertical of the truss. The outermost 30-inch panel (formed by the two outermost diagonals) will permit round ducts up to 7.375, 8.875 and 10 inches for 12, 14 and 16 inch truss depths IF the truss plate joining the two webs together is narrow enough that it does not extend into that opening – at ends of trusses, it is not unusual for the truss plate to extend into that opening. Since the plates usually get smaller as you move away from the bearing, these sizes should be possible in subsequent panels further from the bearing. For 4×2 trusses with Fan-style webbing, a.k.a. modified W
